Regarding the technique of producing a compound semiconductor epitaxial wafer for electronic devices, a study of a method for producing a semiconductor epitaxial wafer with a GaN film formed on a Si substrate by epitaxial growth, the method that can improve the electrical characteristics thereof, in particular, a leakage current in a longitudinal direction, is conducted.
In such a study, after the production of a semiconductor epitaxial wafer, a device is fabricated on the front surface of the semiconductor epitaxial wafer and the electrical characteristics are then evaluated.
In the past, it has been assumed that a flat surface of a base on which epitaxial growth is to be performed is preferable in performing epitaxial growth.
For instance, Patent Document 1 mentions the roughness of an AlN layer of an initial layer and discloses setting the surface roughness Ra of a silicon substrate in contact with the AlN layer at 0.2 to 1 nm and thereby improving the crystallinity of a group-III nitride semiconductor which is grown above the silicon substrate. However, Patent Document 1 makes no mention of electrical characteristics.